An internal combustion engine may be operated to vary a lambda value based on requested operating conditions. A low lambda value corresponds to a rich operation, wherein a rich operation is used for the release and conversion of trapped NOx in aftertreatment devices as well as for release of sulfur at relatively lower bed temperatures. The transition of the lambda value to a lower value, i.e. a transition from lean to rich operation, leads to higher wet soot production. This wet soot may be deposited on the exhaust-gas components downstream of the exhaust manifold, such as the turbocharger rotor shaft, degrading their operating characteristics and performance.
One approach to reduce soot deposits on exhaust-gas components is shown by Linder et al. in DE 3235953 A1. Therein, a filter is positioned close to the exhaust side of the internal combustion engine. A bypass line and bypass valve are connected to the filter. At a full-load operation, the bypass line is closed via the bypass valve and the exhaust gas is passed through the filter. At other load conditions, the bypass line is opened via the bypass valve and the exhaust gas is passed through the bypass line, bypassing the filter. Another approach is shown by Gudorf et al. in EP 2105596 A2. Therein, a filter is positioned upstream of the turbocharger turbine. Here, the exhaust flows through the filter during operation of the internal combustion engine.
A potential issue noted by the inventors with the above approach of Linder et al. is that the filter is engaged only at full load. Therefore, soot may still pass to the downstream components during other engine operating conditions. Another potential issue noted by the inventors with the approach of Gudorf et al. is that no flow control is provided. The exhaust flow must pass through the filter, and airflow to the turbocharger turbine may be decreased during engine operation.
One potential approach to at least partially address some of the above issues includes an exhaust aftertreatment device positioned in an exhaust manifold of an exhaust system of an internal combustion engine. The exhaust aftertreatment device comprises a filter passage formed by a first filter element and a second filter element which form a through-path that is variably adjustable in response to a lambda value. The filter passage filtration walls are adjustable in terms of their relative spacing with respect to one another. Thus, the exhaust flow is filtered upstream of other exhaust gas components and the exhaust flow passage volume is controllable based on an engine operating condition.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.